JPH01188471A - Production of silicon nitride sintered body - Google Patents

Production of silicon nitride sintered body

Info

Publication number
JPH01188471A
JPH01188471A JP63011098A JP1109888A JPH01188471A JP H01188471 A JPH01188471 A JP H01188471A JP 63011098 A JP63011098 A JP 63011098A JP 1109888 A JP1109888 A JP 1109888A JP H01188471 A JPH01188471 A JP H01188471A
Authority
JP
Japan
Prior art keywords
powder
mullite
sintering
silicon nitride
sintered body
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP63011098A
Other languages
Japanese (ja)
Other versions
JPH0772107B2 (en
Inventor
Teizo Hase
長谷 貞三
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Motor Corp
Original Assignee
Toyota Motor Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Motor Corp filed Critical Toyota Motor Corp
Priority to JP63011098A priority Critical patent/JPH0772107B2/en
Publication of JPH01188471A publication Critical patent/JPH01188471A/en
Publication of JPH0772107B2 publication Critical patent/JPH0772107B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/58Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
    • C04B35/584Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Ceramic Products (AREA)

Abstract

PURPOSE:To obtain the subject sintered body having superior strength at high temp. by mixing Si3N4 powder with a specified amt. of mullite powder and Y2O3 powder as sintering assistants, molding the mixture and sintering the molded body in a nonoxidizing atmosphere. CONSTITUTION:94-99.2wt.% Si3N4 powder based on alpha-Si3N4 and having 0.1-1mum particle size is mixed with 0.8-6wt.%, in total, of high purity mullite powder and Y2O3 powder each having a particle size equal to or smaller than that of the Si3N4 powder in 2/1-1/1 ratio of mullite/Y2O3. The mullite powder consists of 71.6-72.0wt.% Al2O3 and 28.0-28.4wt.% SiO2, has >=99.9% purity and hardly contains impurity metals. The mixture is molded to a prescribed shape and the molded body is sintered at 1,650-1,850 deg.C in a nonoxidizing atmosphere.

Description

【発明の詳細な説明】 [産業上の利用分野] 本発明は窒化珪素焼結体の製造方法に関し、詳しくは高
温における強度に優れた窒化珪素焼結体の製造方法に関
するものである。
DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a silicon nitride sintered body, and more particularly to a method for manufacturing a silicon nitride sintered body that has excellent strength at high temperatures.

[従来の技術] 窒化珪素焼結体は、耐熱性、耐熱衝撃性および強度に優
れ、かつ非鉄溶融金属に対する高い耐食性を有するため
、近年各種分野に用いられている。
[Prior Art] Silicon nitride sintered bodies have been used in various fields in recent years because they have excellent heat resistance, thermal shock resistance, and strength, and high corrosion resistance against nonferrous molten metals.

しかしながら、窒化珪素粉末単独では焼結が困難である
ために、従来各種の焼結助剤を利用した窒化珪素焼結体
の製造方法が提案されている。
However, since it is difficult to sinter using silicon nitride powder alone, methods for producing a silicon nitride sintered body using various sintering aids have been proposed.

例えば特公昭49−21091号公報には、アルミナ(
A叉to3)と酸化イツトリウム(Yz03)とを焼結
助剤として用いる製造方法が、特公昭52−3649号
公報には■a族酸酸化物アルミナとを焼結助剤として用
いる製造方法が、特公昭52−45724号公報にはア
ルミナ、酸化珪素(Si02)および酸化チタン(Ti
Oz>を焼結助剤として用いる製造方法が、それぞれ開
示されている。また、他の化合物として、マグネシア(
MqO)、ジルコニア(ZrO2)、あるいはMqAl
zOaなどが知られ、これらの化合物並びに先述の各公
報に開示の化合物を1種あるいは2種以上組合せて焼結
助剤として用いられている。
For example, in Japanese Patent Publication No. 49-21091, alumina (
Japanese Patent Publication No. Sho 52-3649 describes a manufacturing method using a group A to 3) and yttrium oxide (Yz03) as a sintering aid; Japanese Patent Publication No. 52-45724 discloses alumina, silicon oxide (Si02) and titanium oxide (Ti).
A manufacturing method using Oz> as a sintering aid is disclosed. In addition, as other compounds, magnesia (
MqO), zirconia (ZrO2), or MqAl
zOa and the like are known, and one or a combination of two or more of these compounds and the compounds disclosed in the above-mentioned publications are used as a sintering aid.

[発明が解決しようとする課題] 上記した各種酸化物は、窒化珪素粒子表面に酸化膜層と
して存在する酸化珪素と加熱により反応して液相を生成
する。これにより物質輸送が促進きれ、焼結体の密度が
向上するものと考えられている。従って特公昭52−4
5724号公報などに見られるように、酸化珪素の添加
も焼結促進に有効である。しかしながら、酸化珪素は焼
結後珪酸塩ガラスとして結晶粒子間に残留し、800℃
以上の高温における焼結体の機械的強度を低下させる原
因となっている。そのため1200℃で45kg/mm
2の曲げ強度を有するような、高温における強度に優れ
た焼結体を製造することは困難であった。
[Problems to be Solved by the Invention] The various oxides described above react with silicon oxide present as an oxide film layer on the surface of silicon nitride particles by heating to generate a liquid phase. It is believed that this promotes mass transport and improves the density of the sintered body. Therefore, the special public interest public corporation Sho 52-4
As seen in Japanese Patent No. 5724, addition of silicon oxide is also effective in promoting sintering. However, silicon oxide remains between crystal grains as silicate glass after sintering, and
This causes a decrease in the mechanical strength of the sintered body at higher temperatures. Therefore, 45kg/mm at 1200℃
It has been difficult to produce a sintered body with excellent strength at high temperatures, such as a bending strength of 2.

なお、上記した酸化物と酸化珪素との間で生成されるガ
ラス相を結晶化させるために、上記特公昭52−457
24号などには、焼結後所定温度で加熱処理する方法が
開示されている。しかし焼結体を再度加熱することは、
工数、エネルギー面で不具合がある。
In addition, in order to crystallize the glass phase generated between the above-mentioned oxide and silicon oxide, the above-mentioned Japanese Patent Publication No. 52-457
No. 24, etc., discloses a method of performing heat treatment at a predetermined temperature after sintering. However, heating the sintered body again
There are problems in terms of man-hours and energy.

本発明は上記事情に鑑みてなされたものであり、鋭意研
究の結果、再加熱を不要とするとともに、高温における
強度に浸れた窒化珪素焼結体を製造できる焼結助剤の種
類と量のrF1適値を見出して本発明を完成したもので
ある。
The present invention has been made in view of the above circumstances, and as a result of intensive research, it has been found that the type and amount of sintering aids can be used to eliminate the need for reheating and to produce a silicon nitride sintered body with high strength at high temperatures. The present invention was completed by finding an appropriate value for rF1.

[課題を解決するための手段] 本発明の窒化珪素焼結体製造方法は、窒化珪素粉末94
〜99.2重M%と、ムライト(3AJ2203・2S
iOz)粉末および酸化イツトリウム(Y2O2)粉末
の合計ff10.8〜6重量%と、を混合して所定形状
の成形体を成形する成形工程と、 成形体を非酸化性雰囲気下で加熱して焼結する焼結工程
と、よりなることを特徴とする。
[Means for Solving the Problems] The method for manufacturing a silicon nitride sintered body of the present invention includes silicon nitride powder 94
~99.2 weight M% and mullite (3AJ2203/2S
a molding step of mixing a total of 10.8 to 6% by weight of yttrium oxide (Y2O2) powder and yttrium oxide (Y2O2) powder to form a molded body into a predetermined shape; and heating and sintering the molded body in a non-oxidizing atmosphere. It is characterized by a sintering process of sintering.

窒化珪素粉末としては、通常α−3i3N+が用いられ
るが、β相を含有していてもよい。その粒子径としては
従来と同様に0.1〜1μmのものが好適である。
As the silicon nitride powder, α-3i3N+ is usually used, but it may contain β phase. The particle diameter is preferably 0.1 to 1 μm as in the conventional case.

本発明の最大の特徴は、焼結助剤としてムライト粉末と
酸化イツトリウム粉末とを併用するところにある。ムラ
イトとしては、不純物金属をほとんど含有しない、高純
度のものを用いるのが望ましい。なかでもA文go37
1.6〜72.0重量およびS i Ot 28.O〜
28.4重ff1%T−1純度99.9%以上のものが
最適である。このムライトは、シリマナイト族鉱物を加
熱する方法、アルミニウム化合物とシリカ化合物とを同
時に加熱して合成する方法などにより形成することがで
きる。その粒子径は0.1〜1μmの5i3Nn粉末に
対し同程度か、それより細かい方が好ましい。
The greatest feature of the present invention is that mullite powder and yttrium oxide powder are used together as sintering aids. It is desirable to use mullite of high purity, which contains almost no impurity metals. Among them, A sentence go37
1.6-72.0 Weight and S i Ot 28. O~
28.4 fold ff1% T-1 purity of 99.9% or more is optimal. This mullite can be formed by a method of heating a sillimanite group mineral, a method of synthesizing an aluminum compound and a silica compound by heating them simultaneously, or the like. The particle size is preferably about the same as or smaller than that of 5i3Nn powder of 0.1 to 1 μm.

酸化イツトリウムは、従来より焼結助剤として用いられ
ているものをそのまま用いることができる。その粒子径
は0.1〜1μmの5isN*粉末に対し同程度か、そ
れより細かい方が好ましい。
Yttrium oxide that has been conventionally used as a sintering aid can be used as is. The particle size is preferably about the same as or smaller than that of 5isN* powder of 0.1 to 1 μm.

ムライト粉末と酸化イツトリウム粉末は、合計で0.8
〜6重・潰%となるように窒化珪素粉末と混合される。
The total amount of mullite powder and yttrium oxide powder is 0.8
It is mixed with silicon nitride powder so that the weight is ~6%.

この合計量が0.8重量%より少ないと焼結温度が上昇
して、窒化珪素の昇華分解が生じるようになる。また6
重量%より多くなると、得られる焼結体の高温における
強度が低下する。
If this total amount is less than 0.8% by weight, the sintering temperature will rise, causing sublimation and decomposition of silicon nitride. Also 6
When the amount exceeds % by weight, the strength of the obtained sintered body at high temperatures decreases.

なお、ムライトと酸化イツトリウムの混合比率は、重分
比で2二1〜1:1の範囲にあることが望ましい。この
範囲をはずれると高温における強度が低下する場合があ
る。
The mixing ratio of mullite and yttrium oxide is preferably in the range of 221 to 1:1 in terms of weight ratio. Outside this range, the strength at high temperatures may decrease.

成形工程は、上記窒化珪素粉末、ムライト粉末および酸
化イツトリウム粉末を混合した後、成形して所定形状の
成形体を成形する工程である。圧縮成形、スリップキャ
スティング成形など、従来利用されている成形法を利用
することができる。
The molding step is a step in which the silicon nitride powder, mullite powder, and yttrium oxide powder are mixed and then molded to form a molded body of a predetermined shape. Conventionally used molding methods such as compression molding and slip casting molding can be used.

焼結工程は、成形工程で成形された成形体を非酸化性雰
囲気下で加熱して焼結する工程である。
The sintering process is a process of heating and sintering the compact formed in the forming process in a non-oxidizing atmosphere.

なお、加熱温度は1650〜1850℃の範囲が望まし
い。1650℃より低いと焼結が困難となり、1850
℃より高くなると窒化珪素の昇華分解が生じるようにな
る。
Note that the heating temperature is preferably in the range of 1650 to 1850°C. If the temperature is lower than 1650℃, sintering becomes difficult;
If the temperature is higher than ℃, sublimation and decomposition of silicon nitride will occur.

[発明の作用および効果] 本発明の窒化珪素焼結体の製造方法では、焼結助剤とし
てムライトと酸化イツトリウムが併用される。これによ
り焼結が促進されるとともに高温における強度が向上す
る。この理由は明らかではないが、焼結時にはYtO3
−Aλ203−8iO2系の液相を生成し、従来より少
量の添加であっても焼結を促進し、また冷が固化時には
、酸化珪素はメリライトやムライトとして結晶化して粒
界に残留するため、高温における強度が向上するものと
考えられる。
[Operations and Effects of the Invention] In the method for producing a silicon nitride sintered body of the present invention, mullite and yttrium oxide are used in combination as sintering aids. This promotes sintering and improves strength at high temperatures. The reason for this is not clear, but during sintering, YtO3
-Aλ203-8iO2-based liquid phase is generated, promoting sintering even when added in a smaller amount than before, and when cooling solidifies, silicon oxide crystallizes as mellite or mullite and remains at grain boundaries. It is thought that the strength at high temperatures is improved.

すなわち、本発明の製造方法によれば、高い密度を有し
、常温および高温での強度に優れた窒化珪素焼結体を、
工数およびエネルギーの増加無く容易に、かつ確実に製
造することができる。
That is, according to the manufacturing method of the present invention, a silicon nitride sintered body having high density and excellent strength at room temperature and high temperature,
It can be manufactured easily and reliably without increasing man-hours and energy.

[実施例] 以下、実施例により具体的に説明する。[Example] Hereinafter, this will be explained in detail using examples.

(実施例1) (1)成形工程 ジイミドを熱分解して得られた平均粒径約0゜3μmの
α−3i3N4粉末97重邑%と、平均粒径約0.4μ
mのY2O3粉末1重量%と、平均粒径0.15μmの
高純度ムライト粉末2重量%とを、エチルアルコールと
ともに樹脂製ボールミルにて72時間混合する。なお、
5t3Na粉末中には酸素が1.6重量%、金属不純物
が20oppm以下含有されている。Y2O3粉末中に
は不純物が0.1重量%以下含有されている。またムラ
イトは、アルミニウムインプロキシド(Affi(OC
2Hう)3)とテトラエトキシシラン(Si (OC2
H5)4)を原料としたゾル−ゲル法で合成され、X線
回折の結果から結晶相ムライト(3A文tO3・2Si
Oz)と同定された。
(Example 1) (1) Molding process 97% α-3i3N4 powder with an average particle size of about 0°3 μm obtained by thermally decomposing diimide and an average particle size of about 0.4 μm.
1% by weight of Y2O3 powder of m and 2% by weight of high purity mullite powder with an average particle size of 0.15 μm are mixed together with ethyl alcohol in a resin ball mill for 72 hours. In addition,
The 5t3Na powder contains 1.6% by weight of oxygen and 20 oppm or less of metal impurities. Impurities are contained in the Y2O3 powder in an amount of 0.1% by weight or less. Mullite is also produced by aluminum improxide (Affi (OC)).
2H)3) and tetraethoxysilane (Si (OC2
It was synthesized by the sol-gel method using H5)4) as a raw material, and the results of X-ray diffraction revealed that the crystalline phase mullite (3A tO3 2Si
Oz).

また化学分析の結果、AJ203は71.6〜72.0
重量%、5iOzは28.0〜28.4重間%であり、
不純物は0.03重階%以下である。
Also, as a result of chemical analysis, AJ203 is 71.6-72.0
Weight %, 5iOz is 28.0 to 28.4 weight %,
Impurities are 0.03% by weight or less.

上記混合物からエチルアルコールを蒸溜除去し、さらに
150℃に加熱して乾燥後、100ka/cm”の圧力
で1次成形し、次いで3000kg/cm’で静水圧成
形して所定形状の成形体を成形した。
Ethyl alcohol is removed by distillation from the above mixture, and after drying by further heating to 150°C, primary molding is carried out at a pressure of 100 ka/cm', and then isostatic pressing is carried out at 3000 kg/cm' to form a molded article of a predetermined shape. did.

(2)焼結工程 この成形体を、昇温速度2℃/分、圧力1気圧の条件で
窒素ガス中で1760℃まで加熱し、1760℃に到達
した後さらに9.5気圧まで加圧して4時間保持して焼
結した。
(2) Sintering process This molded body is heated to 1760°C in nitrogen gas at a temperature increase rate of 2°C/min and a pressure of 1 atm, and after reaching 1760°C, it is further pressurized to 9.5 atm. It was held for 4 hours and sintered.

(3)試験 得られた焼結体は、密度、室温での曲げ強度、さらに1
000℃および1200℃における曲げ強度が測定され
、結果を表に示す。なお、密度はn−ブチルアルコール
を用いたアルキメデス法により測定し、曲げ強度はJ 
l5−R1601に従って測定した。高温での曲げ強度
は、炭化珪素製治具を用い窒素ガス1気圧下で測定した
(3) The sintered body obtained by the test has density, bending strength at room temperature, and 1
The bending strength at 000°C and 1200°C was measured and the results are shown in the table. Note that the density was measured by the Archimedes method using n-butyl alcohol, and the bending strength was determined by J
Measured according to 15-R1601. The bending strength at high temperature was measured under 1 atmosphere of nitrogen gas using a silicon carbide jig.

表より、本実施例の製造方法により得られた焼結体は、
理論密度の98.8%の密度を有し、高温における強度
にも優れていることがわかる。なお、この焼結体の気孔
は大部分が閉気孔であった。
From the table, the sintered body obtained by the manufacturing method of this example is:
It can be seen that it has a density of 98.8% of the theoretical density and has excellent strength at high temperatures. Note that most of the pores in this sintered body were closed pores.

(他の実施例、比較例) ムライト粉末および酸化イツトリウム粉末の配合量を表
に示すように種々変化させ、実1NI941と同様にし
て成形、焼結し、同様に試験して結果を表に示す。表よ
り、実施例の焼結体は、理論密度の少なくとも95%の
密度を有している。またムライトと酸化イツトリウムの
混合比率が2=1〜1:1の範囲にあれば、1200℃
においても曲げ強度が45kG/mm2以上と高い値を
示し、高温における強度に特に優れている。さらに、両
者の合計量が少なくなるにつれて焼結温度が高くなって
いることもわかる。
(Other Examples and Comparative Examples) The blending amounts of mullite powder and yttrium oxide powder were varied as shown in the table, molded and sintered in the same manner as Example 1 NI941, and tested in the same manner, and the results are shown in the table. . From the table, the sintered bodies of the examples have a density of at least 95% of the theoretical density. Also, if the mixing ratio of mullite and yttrium oxide is in the range of 2 = 1 to 1:1, the temperature will rise to 1200℃.
It also shows a high bending strength of 45 kG/mm2 or more, and is particularly excellent in strength at high temperatures. Furthermore, it can be seen that the sintering temperature becomes higher as the total amount of both decreases.

特許出願人  トヨタ自動車株式会社 代理人   弁理士   大川 宏Patent applicant: Toyota Motor Corporation Agent: Patent Attorney Hiroshi Okawa

Claims (1)

【特許請求の範囲】[Claims] (1)窒化珪素粉末94〜99.2重量%と、ムライト
(3Al_2O_3・2SiO_2)粉末および酸化イ
ットリウム(Y_2O_3)粉末の合計量0.8〜6重
量%と、を混合して所定形状の成形体を成形する成形工
程と、 該成形体を非酸化性雰囲気下で加熱して焼結する焼結工
程と、よりなることを特徴とする窒化珪素焼結体の製造
方法。
(1) A molded product of a predetermined shape by mixing 94 to 99.2% by weight of silicon nitride powder and a total amount of 0.8 to 6% by weight of mullite (3Al_2O_3.2SiO_2) powder and yttrium oxide (Y_2O_3) powder 1. A method for manufacturing a silicon nitride sintered body, comprising: a molding step of molding the molded body; and a sintering step of heating and sintering the molded body in a non-oxidizing atmosphere.
JP63011098A 1988-01-21 1988-01-21 Method for manufacturing silicon nitride sintered body Expired - Lifetime JPH0772107B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP63011098A JPH0772107B2 (en) 1988-01-21 1988-01-21 Method for manufacturing silicon nitride sintered body

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP63011098A JPH0772107B2 (en) 1988-01-21 1988-01-21 Method for manufacturing silicon nitride sintered body

Publications (2)

Publication Number Publication Date
JPH01188471A true JPH01188471A (en) 1989-07-27
JPH0772107B2 JPH0772107B2 (en) 1995-08-02

Family

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62153168A (en) * 1985-07-30 1987-07-08 京セラ株式会社 Silicon nitride base sintered body and manufacture

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62153168A (en) * 1985-07-30 1987-07-08 京セラ株式会社 Silicon nitride base sintered body and manufacture

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